Add a base class to Wav{Reader,Writer} to access shared parameters.

webrtc/common_audio/wav_file.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_COMMON_AUDIO_WAV_FILE_H_
 #define WEBRTC_COMMON_AUDIO_WAV_FILE_H_
 
 #ifdef __cplusplus
 
 #include <stdint.h>
 #include <cstddef>
 #include <string>
 
+#include "webrtc/base/constructormagic.h"
+
 namespace webrtc {
 
+// Interface to provide access to WAV file parameters.
+class WavFile {
+ public:
+  virtual int sample_rate() const = 0;
+  virtual int num_channels() const = 0;
+  virtual uint32_t num_samples() const = 0;

[kwiberg-webrtc, 2015/08/24 12:13:48]

One might argue that these should have CamelCase names, since the implementation
is by design decoupled from the implementation.

[Andrew MacDonald, 2015/08/24 19:50:57]

A not unreasonable argument, but I would counter that the existing style
correctly hints implementors to make these cheap.

+};
+
 // Simple C++ class for writing 16-bit PCM WAV files. All error handling is
 // by calls to CHECK(), making it unsuitable for anything but debug code.
-class WavWriter {
+class WavWriter final : public WavFile {
  public:
   // Open a new WAV file for writing.
   WavWriter(const std::string& filename, int sample_rate, int num_channels);
 
   // Close the WAV file, after writing its header.
   ~WavWriter();
 
   // Write additional samples to the file. Each sample is in the range
   // [-32768,32767], and there must be the previously specified number of
   // interleaved channels.
   void WriteSamples(const float* samples, size_t num_samples);
   void WriteSamples(const int16_t* samples, size_t num_samples);
 
-  int sample_rate() const { return sample_rate_; }
-  int num_channels() const { return num_channels_; }
-  uint32_t num_samples() const { return num_samples_; }
+  int sample_rate() const override { return sample_rate_; }
+  int num_channels() const override { return num_channels_; }
+  uint32_t num_samples() const override { return num_samples_; }
 
  private:
   void Close();
   const int sample_rate_;
   const int num_channels_;
   uint32_t num_samples_;  // Total number of samples written to file.
   FILE* file_handle_;  // Output file, owned by this class
+
+  DISALLOW_COPY_AND_ASSIGN(WavWriter);
 };
 
 // Follows the conventions of WavWriter.
-class WavReader {
+class WavReader final : public WavFile {
  public:
   // Opens an existing WAV file for reading.
   explicit WavReader(const std::string& filename);
 
   // Close the WAV file.
   ~WavReader();
 
   // Returns the number of samples read. If this is less than requested,
   // verifies that the end of the file was reached.
   size_t ReadSamples(size_t num_samples, float* samples);
   size_t ReadSamples(size_t num_samples, int16_t* samples);
 
-  int sample_rate() const { return sample_rate_; }
-  int num_channels() const { return num_channels_; }
-  uint32_t num_samples() const { return num_samples_; }
+  int sample_rate() const override { return sample_rate_; }
+  int num_channels() const override { return num_channels_; }
+  uint32_t num_samples() const override { return num_samples_; }
 
  private:
   void Close();
   int sample_rate_;
   int num_channels_;
   uint32_t num_samples_;  // Total number of samples in the file.
   uint32_t num_samples_remaining_;
   FILE* file_handle_;  // Input file, owned by this class.
+
+  DISALLOW_COPY_AND_ASSIGN(WavReader);
 };
 
 }  // namespace webrtc
 
 extern "C" {
 #endif  // __cplusplus
 
 // C wrappers for the WavWriter class.
 typedef struct rtc_WavWriter rtc_WavWriter;
 rtc_WavWriter* rtc_WavOpen(const char* filename,
                            int sample_rate,
                            int num_channels);
 void rtc_WavClose(rtc_WavWriter* wf);
 void rtc_WavWriteSamples(rtc_WavWriter* wf,
                          const float* samples,
                          size_t num_samples);
 int rtc_WavSampleRate(const rtc_WavWriter* wf);
 int rtc_WavNumChannels(const rtc_WavWriter* wf);
 uint32_t rtc_WavNumSamples(const rtc_WavWriter* wf);
 
 #ifdef __cplusplus
 }  // extern "C"
 #endif
 
 #endif  // WEBRTC_COMMON_AUDIO_WAV_FILE_H_